The Vikings’ final loss of the season felt familiar and welcome as a recurring credit card charge.

In the NFC Championship Game following the 2017 season, the final game of the 2018 season and Saturday’s playoff loss to San Francisco, the Vikings have been outscored by a combined 85-27.

Their offensive woes in those games are troubling. Their defensive lapses are startling, because coach Mike Zimmer was hired on the strength of his reputation as a defensive savant, the franchise spent most of its assets in his early years building his defense.

That group peaked the 2017 regular season by giving up fewer total yards than any team in the NFL. In 2018, the Vikings ranked fourth in yards against. This year, the Vikings ranked 14th.

Zimmer should examine whether he works his defenders too hard in practice late in seasons. Too often in their past three season-ending losses, his defense — even his most exceptional players — looked a step slow or simply tired.

The 49ers are a quality team, but they shouldn’t have outclassed the Vikings the way they did, often simply driving Vikings defenders backward so their backs could gain 6 to 8 yards merely by running hard and falling forward.

What is certain is that the defense that peaked in 2017 will be overhauled, in some cases by choice and in some by necessity. For all of Zimmer’s regular-season accomplishments, he will enter 2020 needing to prove that he can win with a new defense. It’s not a given.

Zimmer’s defensive problems are highlighted by the position in which he has invested the most — cornerback. Xavier Rhodes is in steep decline and has a $12.9 million cap hit for the 2020 season. There is no way he’s back at full price, and the way he played this year, he probably shouldn’t be back at any price.

But if the Vikings move on from Rhodes, that would make Trae Waynes their top corner. He performed poorly this season and is an unrestricted free agent. Do you pay big money to someone who you know isn’t worth that money?

Logic dictates bringing either Rhodes or Waynes back, but either move likely would result in regret. The rest of the cornerbacks are a source of angst.

Mackensie Alexander is an unrestricted free agent and expected to leave. Former first-round draft pick Mike Hughes appears to have a serious neck injury. Who knows if he can even be counted on for 2020? Holton Hill is talented but went undrafted because of character concerns and served an eight-game suspension this year for use of performance-enhancing drugs.

So a team featuring three cornerbacks drafted in the first round probably will have to spend another first-round pick on a cornerback despite obvious needs on the offensive line.

The Vikings safeties — Harrison Smith and Anthony Harris — are exceptional, but Harris is an unrestricted free agent and should make big money. Can and will the Vikings invest heavily in a second safety when they have so many other needs?

On the defensive line, Everson Griffen likely will depart and Linval Joseph is no longer the dominant player he once was. My guess is that the Vikings will ask Joseph to take a pay cut.

Danielle Hunter, Eric Kendricks and Smith are stars. Harris and Anthony Barr are high-quality players, even if a player with Barr’s contract should produce more impact plays. The Vikings have defensive line depth and promise in the form of Stephen Weatherly and Ifeadi Odenigbo.

But this team needs cornerback talent and depth, and fresher legs late in the season, and once again rebuilding a faltering Vikings defense falls to Zimmer.

As for General Manager Rick Spielman, he has to cater to Zimmer’s defensive wishes while rebuilding the offensive line, which might require three new starters, and making a franchise-altering decision on whether to sign running back Dalvin Cook to an expensive contract extension.

Cook has one year remaining on his deal, has played in 29 of 48 possible games since he entered the league, and belongs to a peer group that believes in holding out and getting financially rewarded.

Do the Vikings spend big on Cook when they have so many defensive problems to address? Do they spend big on a running back after the 49ers proved that you can dominate with the run with readily available backs and a strong offensive line?

Every team faces tough decisions every offseason, but the Vikings haven’t had to deal with this kind of defensive recalibration since Zimmer was a rookie head coach.

Jim Souhan’s podcast can be heard at TalkNorth.com. On Twitter: @SouhanStrib. • jsouhan@startribune.com

Jim Souhan is a sports columnist for the Star Tribune. He has worked at the paper since 1990, previously covering the Twins and Vikings.